We live in Colorado and it also gets very cold here. I have never filled all my lines with antifreeze because a compressor is much simpler for me. After draining everything per Bama Rambler above and blowing out the lines, I put a cup or so of antifreeze in each drain trap (kitchen and bath sinks and shower) and on top of the toilet flapper. I have never had a freeze problem doing it this way and have also never had to smell or taste antifreeze the next time I use the trailer.
However, I do it this way mainly because we take several RV trips a year during winter and spring, so I have to winterize it multiple times each year. That many winterizations a year could get pretty expensive if I did it only with antifreeze.
"Retirement is the best job I ever had!"
2016 Rockwood Signature Ultra Lite 8244WS 5th Wheel; 2015 Ram 2500 4x4 CC-SB 6.7L CTD
Sold: 2012 Rockwood Mini Lite 2109S